Influence of Phospholipid Fatty Acid Composition of Plasma Membrane of a Self-flocculating Yeast on its Tolerance to Ethanol and the Mechanism

A novel relationship between phospholipid fatty acid composition of plasma membrane and yeast ethanol tolerance, and its mechanism are revealed in this work. When grown with exogenously supplemented fatty acid (0 6 mmol/L), such as palmitic, linoleic or linolenic acid, cells of a self flocculating fusant of Schizosaccharomyces pombe and Saccharomyces cerevisiae were enriched in the kind of added fatty acid in the plasma membranes. After 6 h of exposure to 20% (v/v) ethanol at 30℃, 52%, 18% and 0% of viability levels remained for palmitic, linoleic and linolenic acid enriched cells respectively. When subjected to 15% (v/v) ethanol at 30℃, the equilibrium nucleotide concentration of palmitic acid enriched cells accounted for only 48% and 32% that of linoleic or linolenic acid enriched cells respectively, with its plasma membrane permeability coefficient ( P ′) being only 37% and 20% that of linoleic or linolenic acid enriched cells respectively. Furthermore, both extracellular nucleotide concentration and ( P ′) were lowest in the order of palmitic, linoleic and linolenic acid enriched cells, precisely corresponding to the ranked order of their ethanol tolerances from the highest to the lowest. Thus, the increased ethanol tolerance of palmitic acid enriched cells is closely associated with its ability to maintain a lower plasma membrane permeability when cells are exposed to high concentration of ethanol. ;